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I have a Dell Latitude D520 that lives in my car all the time. Please don't ask about that part, or suggest that the laptop should live indoors. I know this, and I would if I could. Anyhow...

I find that if the outside temperature is below freezing, when I bring the laptop indoors and start it, the laptop runs very slowly. It behaves this way until it is restarted, but only if the restart is after the laptop has warmed to room temperature.

If I start the laptop while it's cold and let it run all day, it still runs as slow as the minute I turned it on. If I restart it at any time after it's warmed up, then it runs like new again.

What causes this? Why does it have to be started or restarted once it's warm? Why doesn't the gradual warming process gradually increase speed?


Edit

The following are proposed answers that I have tried, but to no avail:

  • Turning off SpeedStep to keep the CPU from scaling back its clock rate.
  • Starting the laptop using wall current instead of the cold battery.
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I had a truck like this once, it would not start when it was cold. I installed a block heater, and it worked much better. I think the theory could apply here, but I don't think they make block heaters for laptops. –  Tester101 Dec 4 '09 at 14:59
    
This used to happen to me with a Dell Latitude circa 2000-2002. I'm curious to know the answer. –  Nathan DeWitt Dec 4 '09 at 15:10
    
@tester101: in laptops the CPU is the block heater... –  quack quixote Dec 10 '09 at 14:11
    
Sorry, the CPU is the engine, there is no block heater. –  eleven81 Dec 11 '09 at 13:55
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5 Answers

up vote 6 down vote accepted

The slowdown is caused due to the processor clocking down during boot-up to prevent overheating damage. Paradoxically, laptop CPUs are likely to overheat when booted at cold temperature due to the nature of the cooling assembly used in laptops.

Laptop CPU cooling assemblies usually consist of a flat plate positioned over the CPU and connected by a long copper heatpipe to a heatsink and fan off on the side of the case. Heatpipes contain liquid in a vacuum which provides cooling by capturing heat at the CPU end through vaporization and releasing it at the heatsink end through condensation. It is very likely that in cold temperature, the liquid within the heatpipe freezes and it no longer functions effectively for cooling the CPU until thawed. According to Wikipedia:

Below a certain temperature, the working fluid will not undergo phase change, and the thermal conductivity will be reduced to that of the solid metal casing. One of the key criteria for the selection of a working fluid is the desired operational temperature range of the application. The lower temperature limit typically occurs a few degrees above the freezing point of the working fluid.

This would not happen in a desktop since the heatsink is in actual contact with the CPU and can thus absorb and dissipate heat in and of itself. However in laptops where the heatpipe critical for funnelling heat to the heatsink, it is quite possible for the CPU to overheat and become throttled while the heatpipe is warming to operational temperature.

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Virtually all electrical items have an operating temperature range. It's not just the battery that could be affected, but the other resistors and capacitors etc. on the motherboard.

The whole laptop will need to be kept within this temperature range.

I'd go with the insulated bag idea and also leave it to warm up for a few minutes (next to a radiator perhaps) before turning it on.

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Of course, don't put it on the radiator, otherwise it won't start at all. –  Hello71 Aug 23 '10 at 0:36
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Just a guess: Perhaps when the machine starts and the battery is cold it has little power output and therefore the machine enters a power saving mode.

Could you try keeping the battery inside overnight and starting the cold computer with a warm battery?

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Also you could try storing the computer in a insulated bag (sold in the frozen food isle of major supermarkets) that keeps it from fully reaching the outside temperature. –  Chris Nava Dec 4 '09 at 15:25
    
I agree the battery is a very likely candidate. Cold batteries produce less power output and it's possible the machine isn't getting enough juice to keep everything running at the power levels needed. –  BBlake Dec 4 '09 at 17:21
    
It's not the battery. I just tried starting the cold laptop with the battery removed, running on wall current. The results are the same. Thanks for the idea! –  eleven81 Dec 10 '09 at 13:51
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What kind of CPU is in your PC? If it is an Intel and has Speedstep, you might want to check to see if you can disable it in the BIOS, in the event that it is throttling to a lower CPU speed on your cold power cycles.

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The CPU is a Core Duo 1.83 GHz. I have disabled SpeedStep in the BIOS. When I arrive at work on Monday with a cold laptop, I will learn whether or not this was the problem. –  eleven81 Dec 4 '09 at 15:13
    
Disabling SpeedStep in the BIOS did not resolve the problem. Thanks for your help, however. –  eleven81 Dec 9 '09 at 13:15
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I have this same issue on a Dell latitude D620, it seems at if the processor thinks it is running hot maybe? And slows down and tell the fan to kick in, you would think it would run better when cold, it's got to be a bug in the way it detects temp.

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